Allow admin to approve accounts before they can post anything

This feature request is a way to avoid spam accounts in Writefreely, see the full discussion here: How are you dealing with spam? - #8 by mnlg

We would need to create a new user state (e.g. “NeedsApproval”) so only approved accounts can post. An admin user could approve the accounts, this way spammers would not be able of posting anything until they are approved, giving more control to the site’s admin.